body {
  background-color: #ccc;
  display: flex;
  flex-direction: column;
}
body header {
  width: 100%;
  height: 44px;
  text-align: center;
  font-size: 18px;
  line-height: 44px;
}
body main {
  position: relative;
  flex: 1;
  background: url(../../assets/imgs/advertisement-bg.jpg) no-repeat;
  background-position: center;
  background-size: cover;
}
body main .btn {
  position: absolute;
  right: 14px;
  top: 28px;
  width: 105px;
  height: 40px;
  border-radius: 15px;
  padding: 5px 10px;
}
body main .say {
  position: absolute;
  left: calc(50% - 150px);
  bottom: 240px;
  margin: auto;
  width: 300px;
  height: 64px;
  font-size: 40px;
  color: #fff;
  line-height: 64px;
  text-align: center;
  font-weight: bold;
  animation: run 1s linear;
}
@keyframes run {
  0% {
    bottom: 260px;
    font-size: 0px;
    opacity: 0.5;
  }
  25% {
    bottom: 100px;
    opacity: 0.5;
    font-size: 25px;
  }
  25% {
    bottom: 120px;
    opacity: 0.5;
    font-size: 30px;
  }
  50% {
    bottom: 140px;
    opacity: 0.7;
    font-size: 35px;
  }
  100% {
    bottom: 240px;
    opacity: 1;
    font-size: 40px;
  }
}
